This invention relates to a door latch assembly, and particularly to a door latch assembly for use with a dishwashing machine.
Dishwashing machines conventionally include a tub forming an interior washing chamber. A door opening is provided in the tub, and a door is attached to the door opening and hinged at its lower edge for movement between open and closed positions. The upper edge of the door latches to the door frame for holding the door in sealed closure over the door opening.
The door of the dishwasher contains a control panel adjacent its upper end, and within this control panel is electrical circuitry for controlling the operation of the dishwasher. For proper operation the dishwasher should be capable of being placed in an operable condition only during the time that the door is latched, but in an inoperable condition at all times when the door is unlatched. Therefore, the latch assembly should be capable of simultaneously latching the door and placing the control circuitry for the dishwasher in an operable state. When the latch assembly is unlatched, the latch assembly should at the same time disconnect the control circuitry so that the dishwasher will stop operating. Stopping the operation of the machine when the door is unlatched is important to prevent hot water from being sprayed or splashed upon the person opening the door.
Certain problems have been encountered in developing satisfactory door latch assemblies for dishwashers. One difficulty is designing a door latch assembly which occupies a minimum of space so that it can be easily mounted within the interior panels of the door. Another problem is the need for a door latch assembly which provides a positive reliable latching mechanism, while at the same time providing a positive reliable means for connecting and disconnecting the power system of the dishwasher.
One example of a prior latch assembly is shown in U.S. Pat. No. 4,776,620. This device utilizes a cantilevered leaf spring which is attached at one end to the door frame. The leaf spring engages a fixed bolt mounted within the dishwasher door and deflects while camming over the fixed bolt to the latch position. In the latch position, the cantilever spring also engages switches which actuate the power system for the dishwasher when the door is latched. A latch handle on the door is operable to disengage the latch and simultaneously disengage the latch from the switches so that the switches are rendered in an open position, thereby deactuating the power system of the dishwasher.
One disadvantage of the cantilever spring latch mechanism is the variable spring constant inherent in this type of spring. The force exerted on the end of the spring is variable during its travel. Consequently, this type of latch requires a switch which can be placed in a closed condition in response to a lower spring force. Typically, switches capable of responding to lower forces also must be of a reduced power rating.
Another disadvantage of the device shown in U.S. Pat. No. 4,776,620 is that this latch includes a pivoting handle which requires more space front to back and which affects the handle force and travel. It is desirable to provide a more compact handle which slides in a linear direction and which has a one-to-one force and distance relationship.